In wireless networks, e.g. Long Term Evolution (LTE), Wimax IEEE 802.16 or WLAN IEEE 802.11, multiple antenna systems may be employed for enhancing spectral efficiency.
However, the enhancement of spectral efficiency may be achieved also by assigning resources to individual users of a communication in such a way as to exploit their respective differing channel conditions.
This approach may be used in conjunction with multi-antenna techniques and may be realized by using multi-user resource scheduling.
Multi-user scheduling may be combined with Orthogonal Frequency Division Multiplex (OFDM) to arrive at a multi-user OFDM or OFDMA (OFDM Access).
With OFDMA, multiple users may communicate using the same timeslot but being assigned to different frequency resources.
However, the throughput performance of Multiple Input Multiple Output OFDMA (MIMO-OFDMA) systems may be considered to be interference limited. This may be because the throughput performance of a MIMO-OFDMA transmission, in particular the downlink may be limited by interference from adjacent cells.
There may be a need to provide a more efficient throughput.
3GPP (3rd Generation Partnership Project) document, technical specification group radio access network, 3GPP TS 36.211 V8.3.0 describes physical channels and modulation in evolved universal terrestrial radio access (E-UTRA).
The document T. Wirth, A. Forck, S. Wahls, V. Jugnickel, V. Venkatkumar, T. Haustein, H. Wu: “Polarization dependent MIMO gains on multi-user downlink OFDM with a 3GPP LTE air interface in typical urban outdoor scenarios” ITG-WSA 2008, March 2008 describes gain benefits when using cross-polarized antennas as compared to co-polarized antennas at network nodes.
The Document 3GPP TSG RAN WG1 Meeting #52, R1-080693, Sorrento, Italy, Feb. 11-15, 2008, describes single user MIMO Precoder Matrix Indicator feedback and compression and the Fubiny-Study distance criteria.